"Cuba will participate in the BRICS summit for the first time," Diaz-Canel wrote on X, formerly known as Twitter.
The president said he will also visit Angola, Mozambique and Namibia.
The BRICS summit in Johannesburg is expected to be attended by the leaders of Russia, China, India, Brazil and South Africa. Russian President Vladimir Putin is expected to participate in the summit via video link.
In July, South African Foreign Minister Naledi Pandor said that 23 countries had officially expressed their interest in joining BRICS. In May, Belarus applied for membership in the five-nation group.